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<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      /*
              Object.freeze 冻结对象 完全不可变
            */
      let obj = { name: 'test' };
      Object.freeze(obj);
      obj.age = 30;
      console.log(obj.age); // undefined
    </script>
  </body>
</html>
